I have based my code off several tutorials which has culminated what I think is quite a complicated CSS layout. It has a docked footer. The sidebars are turned on dynamically in my template depending if there is content. The site is designed to work in the following scenarios:

I am new to CSS coding, and I have had to make a lot of decisions without really knowing my stuff. I would love to get feedback to see if I can improve this code, especially with regards to making it cleaner, short code or more compatible.